1. Field of the Invention
This invention relates generally to safety pressure relief apparatus, and more particularly, to an improved low pressure rupture disk and assembly.
2. Description of the Prior Art
A variety of safety pressure relief apparatus of the rupture disk type have been developed. Generally, such apparatus include a rupturable member supported between a pair of complimentary supporting members or flanges which are in turn connected to a relief connection in a vessel or system containing fluid pressure. When the fluid pressure within the vessel or system exceeds the design rupture pressure of the rupture member, rupture occurs causing fluid pressure to be relieved from the vessel or system.
Rupture disk assemblies including concave-convex reverse buckling rupture disks have been developed and used heretofore. Such disks have thicknesses and configurations such that they reverse when predetermined fluid pressures are exerted on the convex sides thereof. Prior to reversal, a reverse buckling rupture disk is in compression which allows the operating fluid pressure exerted on the disk to be relatively close to the pressure at which the disk is designed to reverse. Upon reversal, the disk ruptures thereby relieving pressurized fluid from the vessel or system being protected.
In order to prevent the formation of loose pieces upon rupture, reverse buckling rupture disk assemblies have heretofore included knife blades upon which the disk impales when reversed. One such knife blade assembly is described in U.S. Pat. No. 3,294,277 to Wood which is assigned to the assignee in the present invention. Another knife blade assembly is described in U.S. Pat. No. 4,236,648 to Wood et al., which is also assigned to the assignee of this present invention. The disclosures of the foregoing patents are incorporated in this description of the present invention by reference.
While the heretofore developed and used reverse buckling rupture disks and assemblies have operated successfully in many applications, problems have been encountered in their use in some low pressure applications. For example, in low pressure applications where vacuum conditions can exist in the vessel or system being protected but the reverse buckling rupture disk must still reverse and relieve pressure when a positive low pressure is exerted thereon, the material from which the disk is formed must be very thin, e.g., a 1 inch in diameter reverse buckling rupture disk designed to be subjected to vacuum conditions but rupture at a positive pressure below about 25 psig must be formed of stainless steel or the like having a thickness in the range of from about 1 to about 2 thousandths of an inch. As a result of the thin material from which the disk is formed, the reverse pressure brought about by the vacuum quickly causes deformation of the disk which in turn brings about premature failure or improper operation thereof.
By the present invention, improved low pressure rupture disks and rupture disk assemblies are provided wherein the rapid distortion and weakening of the disks when subjected to high heat, vacuums or other reverse or cyclic pressure conditions are prevented.